1. As a forger I would like to see a large open world like forge world with at least a land, underground, and space area to forge in, like sandbox just waaaay bigger.
2. Bring back some of the great gametypes like invasion. Also perhaps being able to forge firefight maps would be great, or space battles.
3. Multiple characters to play as. ex. Forerunners/covenant. Not just Spartans because then it just get somewhat boring. And if you do add more characters to play as make them fully customization like a spartan.
4. More bloody vehicles for forge! the forging community has been asking for things like pelicans to forge since halo 3, also bring back another human air vehicle, I con't understand why you would remove the falcon when it balanced with the banshee nicely. And if you are keeping the mantis then make another covenant vehicle that equals to that.
5. A more interactive and longer campaign. I beat halo 4's campaign on legendary in 10 hours. Come on you should make it so the campaign takes more like 15 hours on normal mode.
6. Bring firefight back! Spartan ops is great, but the maps are repetitive and I isn't as much fun, plus there's no scoring system with it. In firefight I could spend 3 hours with my friends playing legendary and still not get bored.
7. Don't be so prideful 343 you removed alot of great things from halo that people loved because you didn't want to be so much like bungie.
8. No rotating weekly gametypes! i dislike how I could only play team snipers for one week, compared to Reach wear I could play it anytime I want. It really frustrates me that I have to wait for my favorite gametypes.
These are some of the biggest things that are bothering me right now...